MATLAB: How to construct this vector without loop

MATLABvector

Hi, everyone:
I was wondering, is it possible to construct following vector without for loop?
A=[1 2 3 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 …..]
or equivalently A=[1:(3*1), 1:(3*2), 1:(3*3), 1:(3*4), …., 1:(3*n)]
Many thanks!

Best Answer

Here is flexible version not using cell2mat:
n = 4 ; % user specified
V = 3 ; % as in the example -> [1:V 1:2*V ... 1:n*V]
ix = V*[1:n]
A = ones(1,sum(ix))
ix =ix(1:n-1)
A(cumsum(ix)+1)=-ix+1
A = cumsum(A) % result
Related Question